Engine integration is one of the most difficult tasks in the aerodynamic design of an underwing podded engine aircraft. Specifically, it is a principal design goal for the pylon to minimize impacts to the aerodynamic flow around the wing, with minimal weight and complexity.
The channel space between the engine nacelle, pylon, wing and fuselage tends to accelerate the aerodynamic flow thereby producing different aerodynamic impacts. Among these problems are shock waves in the area between pylon, nacelle and wing lower surface, as well as airflow separation in the wing inboard lower surface.
Careful contouring of the pylon minimize the inboard acceleration thereby reducing the drag impact and minimizing the thrust loss. One of the techniques commonly used to improve the flow in this region is to increase the pylon length as much as possible, but an increase in the pylon length disadvantageously increases the pylon weight. Another technique includes providing a fairing in the upper part of the pylon and increase the length of only the pylon/wing fairing. In this regard, the fairing can sometimes be even longer than the wing thereby extending behind the trailing edge of the wing. Such partial pylon extension however still incurs a weight penalty even though to a lesser extent than the weight penalty associated with extending the entire pylon. Furthermore, a complicating factor with such a design alternative is that there may be high lift wing surfaces (e.g., flaps) in this region and therefore any protruding pylon section must also be able to move when the flaps are deployed, which in turn increases system complexity and weight, as well as cost.
One prior proposal for engine pylon fairings is U.S. Pat. No. 5,443,230 (the entire contents being expressly incorporated hereinto by reference) includes providing an airfoil which is curved away from the aircraft in an axial rearward direction and has a portion which is curved toward the aircraft in the vertical direction from the nacelle toward the wing. Another proposal is evident in U.S. Pat. No. 8,336,813 (the entire contents being expressly incorporated hereinto by reference) whereby the pylon is extended rearwardly and has a trailing edge which is shifted toward the root of the wing to which the pylon is mounted.